Need some guidance/advice and this group has always helped me learn!!!

My wife's 2005 Outback 2.5i w/ the 4EAT has developed a heavy vibration most pronounced while accelerating in a straight line. It kicks in a bit around 20mph, but really comes back loud and strong at 40mph and above. Enough to shake the whole interior, make the rearview mirror fuzzy, etc. It is rhythmic, but loud enough to be a strong hum (which is why wheel bearings were checked). It did appear there was irregular tire wear on the RF which will explain some of the repairs attempted, but nothing has cured...

Chased out the following suspects...
Tires (full swap from my 2005 OB that had just been wheel balanced and relatively new, no change)
Propeller shaft (swapped for my old seized one from my 2005 OB which I had redone with servicable U joints and installed, no change)
Found a bit of notchiness in RF wheel bearing, replaced spindle with one with good, smooth bearing...no change
Replaced FR drive shaft/CV axle ... no change.

After doing the CV, was considering doing LF when I thought, hey, why not put in the AWD fuse to disable AWD and leave as FWD only and guess what? Vibration is gone whne fuse is installed.

So, that leaves me with questions...

Is this a failure in the front differential? Transmission Issue? Rear Differential? And how to I effectively wigure out which?

The ATF level looks fine and it is pink, not brown or black. The front differential fluid looked sufficiently filled and nearly clear. Have not yet been able to open rear differential as plugs are super stuck...lots of penetrant on them now, so they may break loose later or when I can get on a hoist to get more leverage.

How would you go about next steps?

And if it is deemed to be a failure requiring transmission removal, I can source a low mileage (say 100K miles) transmission for around $500.  What would a reasonable labor cost be for a transmission swap?

Thanks in advance for all good advice!!! The Subaru community is awesome!

I've read that carrier bearings can really make noise when they are going out.

39 minutes ago, 1 Lucky Texan said:

I've read that carrier bearings can really make noise when they are going out.

Texan - Changing out the propshaft would kind of preclude that issue...

 

how old are the struts?

just did fronts on my 02 forester - they were so bad that I had a TERRIBLE vibration -most pronounced on left front - the wheel was "bouncing" (commonly seen on minivans, usually in the rear...)

About to do rear struts as well, but had to wait for funds availability or they all would have been done at the same time.

Point is, after changing the struts, the vibration is gone.

 

Struts are of unknown age.  I did notice some strange tire wear on the front right tire, almost like a combination of cupping and flat spotting in a random pattern.  That's what precipitated the extra work on the front right.  

 

Hard to believe strut vibration would be affected by the AWD fuse though?!?!?

ok, sorry, missed the bit about the fuse making it disappear..

that is a bit of an odd one...

when you say it "developed" the problem, did this come on slowly or was there a wreck or work done to the car before this began? New tires?

Edited July 30, 20196 yr by 1 Lucky Texan

I thought when she bought the car there was a slight vibration.  She's had it about a year...the vibration seems much stronger now.  That's why I said developed.  No tire changes yet...I was waiting to get the vibe cured so that whatever it was would not destroy a new set of tires!  No wrecks since we've had the car.

 

The only work done was a change out of the RF spindle and change of propeller shaft as noted.

I'm wondering of there's a chance the companion flange or a bearing in the rear diff is wonky...

 

I guess rear wheel bearings need a close inspection.

has the car been driven thru deep water?

No deep water to my knowledge.  When you say rear wheel bearings, I am assuming you mean the LR and RR at the hubs, not bearings in the differential, correct?  And if so, I could probably do so by removing axles and rolling the hub/bearing by hand to check for rough spots, correct?

 

Front CV axles (it’s the inner joint) routinely vibrate under load/acceleration/uphill. 

Bearings routinely make noise and those 2005s have no shortage of failed wheel bearings.  They usually make noise first then vibrate as they progressively get worse and get really bad.  They can be hard to diagnose with no consistent symptoms that always confirm. False negatives are common.  I’ve seen some not have any obvious play until the entire assembly is off and axle is out of it.  

Use a stethoscope.  Check temps after driving and compare drivers and passengers side.  

Rear diff failure is rare and usually a misdiagnosis, that’s a hard one to lean towards without compelling Subaru specific experience.  

I assume you’ve already checked for obvious play, loss ness and front control arm bushings?  The rear bushings on the front are weak. 

On 7/27/2019 at 9:17 AM, matt4irish said:

..heavy vibration most pronounced while accelerating in a straight line. It kicks in a bit around 20mph, but really comes back loud and strong at 40mph and above. Enough to shake the whole interior, make the rearview mirror fuzzy, etc. It is rhythmic, but loud enough to be a strong hum (which is why wheel bearings were checked).

...

After doing the CV, was considering doing LF when I thought, hey, why not put in the AWD fuse to disable AWD and leave as FWD only and guess what? Vibration is gone whne fuse is installed.

These statements SCREAM u-joints. I know you said you swapped shafts, did you replace the joints yourself? Were you careful to maintain the orientation remained the same from the old joints?

 

The FWD fuse basically eliminates any problems in the front end, and almost everything in the transmission. I've never heard a bearing noise (diff or wheel) that I would describe as a vibration, at all. Maybe a rear axle joint, but those fail so infrequently (I don't think I've ever seen one, and they're definitely not common, if available at all, in the aftermarket).

Numbchux was correct.  I had the shaft done by a "reputable shop", but took it out and back to them.  Turns out the shaft was out of balance.  After rebalancing, I reinstalled the shaft.  Smooth as can be again.  Amazing that it was the first thing fixed and had to be redone as the last thing!

 

Thanks everyone for your help!